In another sign of the City returning to business as usual, banks have begun poaching key staff from rivals by offering to buy them out of their promised bonuses, according to research published today.

Despite government calls for the banking industry to show restraint, the number of such "bonus buyouts" has increased fourfold compared with a year ago as bonus season approaches, reports Astbury Marsden, a financial services recruitment company.

It means that bankers and hedge fund managers defecting to other firms will be granted the bonuses that would have been awarded to them by their old employer as a part of their new pay package.

Typically, up to 40% of performance-related bonuses are paid in cash and the remainder in shares, which usually pay out over a period of three to five years. A banker is not entitled to any of these shares if they leave before this period.

But increasing competition for top City talent means many prospective employers are now offering to pay out these bonuses ahead of time, or grant new share options worth the same amount.

Jonathan Nicholson, managing director at Astbury Marsden, said: "Banks are now prepared to buy out 100% of a potential employee's shares or options they have locked up with their current employer."

Four-fifths of new recruitments now involve such bonus buyouts, compared with one in five a year ago. A fifth of these bonuses are bought out by paying the new employee cash upfront, with the rest in the form of new employee shares and share options.

Astbury Marsden said that bonus buyouts have accelerated in the last month as banks try to poach their rivals' best earners before Christmas, when fewer people change jobs.

Deutsche Bank, which reported third quarter results today, said it had set aside €4.6bn (£4bn) in bonus pool for its corporate and investment bank over the first nine months, amounting to €285,000 per employee.

Nicholson added: "Banks and fund managers are confident about next year and they still want to add to their teams. Within reason, they are willing to pay for the talent. A successful trader or banker will now no longer move unless their entire share bonus scheme is bought out. A year ago they would have been more flexible – now they don't want to forgo a penny."

The business secretary, Vince Cable, this week warned bankers against embarking on a "self-indulgent bonus round" as he placed soaring executive pay and potentially destructive takeovers in the spotlight of a new government review into the way the City operates.